Progesterone level only 4.05 at 5 weeks???

Has anyone ever dealt with low progesterone levels in early pregnancy? I had my first appointment today to check my levels and determine how far along I am based off my hcg and progesterone levels, (I’m estimated to be 5 weeks and 1 day right now) my doctor just called with my results and said my hcg is 85.7 and my progesterone is only 4.05…. she told me progesterone levels are supposed to be at at least 11 or 12 to keep the pregnancy going and asked if I’ve started bleeding or anything which I have not. She prescribed me progesterone to start taking and I have to go back next week for more blood work. Has anyone else’s ever been this low and everything be okay? I’m scared I’m gonna have a miscarriage now…